Determining half-relationships with Polynesians – Part II

In my last entry I demonstrated the difficulties of determining the half-relationships after receiving the DNA results of my half-first cousin.   Within an endogamous group, that could be even more difficult as we see larger amounts of DNA shared.

While the ISOGG Wiki Autosomal DNA Statistic page can list the average amount of centimorgans shared,  Blaine Bettinger’s The Shared cM Project  demonstrated that the minimum and maximum amounts shared can vary.  This becomes more evident as the distance of relationship increases.

Within an endogamous group it makes sense that having more than one pair of common ancestors may increase that amount.  The same would apply if you descend from the same common ancestor multiple times.  Both would produce higher amounts shared.

A few months ago I got the results of my aunt believed to be a full-sister of my mother.  My aunt suspected that her father was not her biological father.  And she was right.  But she was not the only one who knew of this, but the rest of the family, particularly the ones of my generations believed that this Aunt’s father was her biological father and did not suspect otherwise.

From my mother’s Family Finder (autosomal) match list at FTDNA:

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The top is my mother’s sister while the one right below it belongs to my half-1st cousin whose father George was mentioned in the last entry – Determining half-relationships with Polynesians.

Initially I was confused by the total amount since I knew it was more than what I shared with two of my half-brothers.  This is how two of my half-brothers compare to me and to each other.

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So my mother and her sister did share a bit on the high-end for half-siblings, but low end for full-siblings.  These are the predicted averages shared for siblings vs. half-siblings.

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The next step was to take a look at the X chromosome.  For half-sisters who had the same father, they would share an entire X chromosome based on how the X is inherited.  To my surprise, it looked like someone took a razor blade and sliced out some pieces of the image.

 

5+cM setting

5+cM setting

 

1+cM

1+cM

For half-sisters they share a lot compared to what I saw when comparing my half-brothers to each and to me.  Also, I decided to include both the default 5+cM setting and the 1+cM.  With my brothers, we hardly get anything when I lower it to 1+cM.  But with my mother and aunt, you can see a difference although chromosomes 4 and 18 are more likely to be IBS, but given the situation (endogamy, small communities, & isolation) it just may be IBD from a very long time ago.

So the X was not helping me one bit since I thought maybe they were areas on the chromosome that could not be read – no calls.

I immediately uploaded to GEDmatch for further analysis.  No surprise that when I looked at the X, it was the same exact thing.   Knowing that it wouldn’t be helpful, I turned to the other 22 pairs of chromosomes.

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What you would be looking for in full-siblings are full-identical regions (FIR) which are the green sections on the bar graph.  Here is an example of my 1st cousins, a brother and sister.

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About 25% will be fully identical.  You can read more about how much full versus half-identical regions siblings would share at ISOGG’s Wiki – Fully Identical Region page.

This is what my mother and aunt showed.

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There are only small chunks of  FIR rather than long segments of it that you would see in full-siblings.  So this confirms a half-sibling relationship.

Recent Founder’s Effect, bottlenecking and 6 Tahitian women on Pitcairn island

I finally got the autosomal results of a Pitcairn resident who has been a member of the Polynesian project for a year now.  Previously I had another member who is a Norfolk island descendant and whose ancestors moved to Norfolk but were originally from Pitcairn.  Another Norfolk descendant tested at another company, but his raw data were uploaded to GEDmatch.com in order to be compared.  Now having that this particular Pitcairn resident tested, I can make a comparison for these 3 people since they all have ties to Pitcairn.

 

HISTORY OF PITCAIRN ISLAND

Pitcairn was settled in 1790 by mutineers of the HMS Bounty and Tahitians1.  The initial population of 27 consisted of 9 mutineers, 6 Tahitian men and 11 Tahitian women along with an infant girl.  Only 6 of the mutineers and 6 Tahitian women would produce descendants.

Mutineers:
1) Fletcher Christian
2) Edward Ned Young
3) John Mills
4) William McCoy
5) Matthew Quintal
6) John Adams

Tahitian women:
1) Mauatua Maimiti
2) Teraura
3) Teio
4) Tevarua2
5) Vahineatua
6) Toofaiti

 

POPULATION GROWTH, DECREASE & RE-POPULATION

The population started with 27 people but only 12 of them would produce descendants.  By 1840 the population exceeded 100, and by the mid-1850s the community was outgrowing the island3.

On May 3, 1850 the entire community left for a 5 week trip and settled on the island of Norfolk on June 8.  Nearly 3 years later 16 of them returned to Pitcairn.

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EFFECTS WITH AUTOSOMAL DNA

I have mentioned in previous blog entries that eastern Polynesians are genetically less diverse than western Polynesians.  So it should be no surprise that Hawaiians and Maoris as well as Tahitians will come up as closer matches to each other despite sharing common ancestors 8 centuries ago.

Now we are looking at two things.  Firstly, a founding population where only 12 people produced offspring, and half of the 12 being Tahitian women, or eastern Polynesians.  And these 12 were not paired off equally.

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They married multiple times, some of them never produced descendants with their other spouses.

Secondly, there was a population bottleneck in 1859.

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In 1856 the population expanded to 193, then the entire population left.  That population was already interrelated just 66 years after the initial 12 founding people started the population.  They all left, but 16 of them returned.  Eventually, a few more returned but the remaining population continued life on Norfolk island while the rest of the Pitcairns were starting the population again. It would take only 23 years to repopulate the island increasing the population to 250.

 

ANALYZING A PITCAIRN RESIDENT’S AUTOSOMAL DNA

The Pitcairn resident descends from all of the 12 founding people.  No surprise, given that small amount plus that was just 225 years ago and 7 generations ago for this particular person.

Although I cannot show with a family tree how many times they descend from the 12 founding people due to size and the complexity of the tree, I decided to list the number of times they descend from each of the 12.

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This resident’s paternal grandparents are 2nd cousins one way, and 3rd cousins another way while their maternal grandparents were 2nd cousins two ways.  There are more ways that they are related going further back as well, but my genealogy software cannot pick up the multiple relationships and it seems to select the closest relationship but selected 2nd cousin once removed, so not sure which line it was picking up.  This person’s maternal grandfather was born on Pitcairn but there is no known genealogy for him.  For their other grandparents, here is who they descend from.  (Founding people in bold)

Paternal grandfather – Christopher Warren, son of George Warren whose mother was Agnes Christian, and Alice Butler whose mother was Alice McCoy.
Paternal grandmother – Mary Christian, daughter of Sidney Christian & Ethel Young.
Maternal grandmother – Ivy Young, daughter of William Young & Mercy Young.

Agnes Christian and Alice McCoy were 2nd cousins, great-granddaughters of Fletcher Christian and Mauatua.  Ivy Young’s parents William and Mercy Young were 2nd cousins two ways to each other.  Great-grandchildren of Edward N. Young and Toofaiti and of Fletcher Christian and Mauatua.

As confusing as it seems, you can imagine how would DNA show up.  After uploading the raw data to GEDmatch.com for further analysis, I immediately ran the “Are Your Parents Related” tool.

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It predicted 3.3 for the most recent common ancestor (MRCA).  Still not sure how to interpret GEDmatch’s MRCA estimation, but in reality, the most recent common ancestor would be their 2nd great-grandparents – Thursday October Christian II and Mary Polly Young.  And there were other Youngs as I previously mentioned and Christians as well.

When I ran my mother’s kit through that same tool, her largest segment was 13.9cM, and there were a total of 5 segments that would total 51.5cM.

Largest segment = 13.9 cM
Total of segments > 7 cM = 51.5 cM
Estimated number of generations to MRCA = 4.1

Unlike the Pitcairn resident whose largest segment was 24.7cM and with 11 segments.  My mother’s parents were from different islands and as far back as I was able to trace their ancestries, they did not intersect nor did their ancestors come remotely near to each other given that they were from 3 different islands.

I would love to get more Pitcairn residents to test, to see if there is any noticeable pattern using this tool, or David Pike’s ROH.  If there is, we definitely could use it in helping to determine a true close genetic match versus an endogamous one.

 

COMPARING TO NORFOLK DESCENDANTS

There are 2 particular matches to many of the Polynesian DNA project’s members and both of these 2 people are descendants of Norfolk residents.  I will refer to them as Norfolk #1 and Norfolk #2.

Norfolk #1’s maternal grandmother was from Norfolk and she was the daughter of Francis Nobbs and Ruth Christian.  Norfolk #2’s maternal grandfather was from there, and his parents were William Adams and Sarah Christian.

A further breakdown where I bold the founding people.

NORFOLK #1
Francis Nobbs’ ancestry, son of Alfred Nobbs & Mary Christian:
Paternal grandfather – George Nobbs
Paternal grandmother – Sarah Christian, daughter of Charles Christian & Tevarua
Maternal grandfather – Benjamin Christian, son of John Buffett & Mary Christian
Maternal grandmother – Eliza Quintal, daughter of John Quintal & Maria Christian

Sarah and Maria Christian were daughters of Charles Christian & Tevarua, while Mary Christian was their 1st cousin.

Ruth Christian’s ancestry, daughter of Isaac Christian & Miriam Young:
Paternal grandfather – Charles Christian, son of Fletcher Christian & Mauatua
Paternal grandmother – Tevarua, daughter of Teio
Maternal grandfather – William Young, son of Edward N. Young & Toofaiti
Maternal grandmother – Elizabeth Mills, daughter of John Mills & Vahineatua

NORFOLK #2
William Adams’ ancestry, son of John Adams & Caroline Quintal:
Paternal grandfather – George Adams, son of John Adams & Teio
Paternal grandmother – Polly Young, daughter of Edward N. Young & Toofaiti
Maternal grandfather – Arthur Quintal, son of Matthew Quintal & Tevarua
Maternal grandmother – Catherine McCoy, daughter of William McCoy & Teio

When comparing the two Norfolk descendants to the Pitcairn resident, I was surprised to see no overlapping segments.

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It is interesting to see how for Norfolk #1, the largest segment is 40.85cM for the largest segment and a total of 134.5cM.  The largest segment is significant, and although Pitcairn & Norfolk #1 are related multiple ways, the closest known relationship makes them 4th cousin once removed.

Comparing Pitcairn to Norfolk #2, the largest segment is 27.3cM, which for Polynesians in general could be pretty distant.  Total shared is 95.1cM.  And just as with Norfolk #1, Norfolk #2 and Pitcairn are related multiple ways, but the closest relationship makes them 4th cousins.

At the moment I cannot compare Norfolk #1 and Norfolk #2, but I am trying to get one that taken care of in order to upload Norfolk #1’s raw data to GEDmatch for further analysis.

I was expecting to see the overlap at least when comparing to the Pitcairn resident given that their ancestors’ have been on the island since the beginning, but it goes to show how unpredictable and random DNA can be.

A list of all 3 and how many times they each descend from the following founding population.

Screen Shot 2015-12-21 at 1.46.23 PM

And while various Polynesians can be compared to all three of these people and may show overlapping segments, there is really no way to map these segments.  These 3 testees would match other project members based on segments inherited by one or more of these 6 Tahitian women that settled on Pitcairn.  And we all would have shared common ancestor(s) from at least 8 centuries ago.

Below I compare the Pitcairn resident to a Hawaiian, a Maori and a Cook Island Maori as well as my Hawaiian mother.  Incidentally, there is a project member whose father was from Tahiti, yet that person does not come up as a match.

(default setting)

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(1+cM setting)

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Comparing Norfolk #1 with the same people with the exception of not being a match to the Cook Island Maori.

(default setting)

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(1+cM setting)

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Norfolk #2 did not test at FTDNA but at 23andme, and although their raw data was uploaded to GEDmatch.com, all the others being compared were not uploaded except for my mother’s raw data.

For additional information about the DNA study of the descendants of the Mutiny on the Bounty, see ‘Mutiny on the Bounty’: the genetic history of Norfolk Island reveals extreme gender-biased admixture.

Footnotes

1. History of the Pitcairn Islands.
2. Pitcairn Settlers lists an additional Tahitian woman known as Sully, as the wife of Matthew Quintal and the mother of Matthew Jr., John, Arthur, Sarah and Jane Quintal. Another source, as well as the Pitcairn resident who got DNA tested, claims that there were only 6 Tahitian women of whom they descend from.  There was no mention of Sully, although Tevarua is listed as being married to Matthew Quintal and the parents of  Matthew Jr., John, Arthur, Sarah, and Jane Quintal.
3. Historical Population of Pitcairn.

East Asian category for Polynesians

My mother told me today that she received from the First District Circuit Court that handled her adoption, the non-indentifying form, which is where it lists her biological parents’ ancestries.  They indicated that both parents are Hawaiian and Chinese.  I find that to be an error since my mother had her DNA tested at 3 companies.  Maybe that was based on an assumption or the biological parents may not have known too much about their ancestries.

At the age of 5, she met her biological father and described him as a “pure Hawaiian.”  This made sense since she gets the following percentages from each company.

Screen Shot 2015-07-13 at 3.25.31 PM

 

So this meant that one parent was just Hawaiian while the other parent was admixed with some European.  Based on all the companies she has tested with and analysis [from Dr. McDonald], my mother gets the following averages.

European = 16%
Oceanian = 25%
East Asian = 55%

Those are based on 23andme, FTDNA’s old Population Finder and Dr. McDonald’s analysis.  FTDNA’s current myOrigin lumped their former Oceania category under Southeast Asia, or the more broader East Asian category.  AncestryDNA however created a Pacific Islander category with the subgroups Polynesia & Melanesia and between myOrigins and Ancestry, the average total is 83%.

In reality, the East Asia category is just one of two components that make up the genome of Polynesians.  The other is Melanesian/Papuan (Oceania).  For Polynesians, autosomally they are 79% East Asian and 21% Melanesian1.

In Population Genetic Structure and Origins of Native Hawaiians in the Multiethnic Cohort Study they applied ADMIXTURE on genome-wide SNP data to finely estimate the degree of admixture in Native Hawaiians.  They found that with Native Hawaiians, “an average of 32% and 68% of their genomes to be derived from Melanesian and Asian origins, respectively”.  But that “[r]ecently, Kayser et al. surveyed the nuclear genome with 377 microsatellite markers in 47 Pacific Islanders and identified 79% Asian and 21% Melanesian proportions of ancestry for Polynesians.”

So while other studies revealed that Polynesian genome consist of 79% Asian and 21% Melanesian components, the study with Hawaiians averaged 32% Melanesian and 68% East Asian2.  The higher amount of Melanesian could be attributed to the repeated bottleneck effects throughout the centuries specifically for eastern Polynesians, i.e. French Polynesians, Rapa Nui, Cook Island Maoris, Maoris from New Zealand and Hawaiians.

My mother averages 25% Oceanian and 55% East Asian.  The two combined equals 80%.  25% (Oceanian) is 31% of the entire Polynesian (80%) percentage.

Just over a year ago I was going through my mother’s matches on GEDmatch and began running their kits through various admixture tools to see their totals of Oceania versus East Asia.  I wanted to see if they fell within the 27% to 32% Melanesian/Papuan/Oceanian.

Screen Shot 2015-07-13 at 5.20.34 PM

This is only a partial list.  There are more lines on the bottom but I am just showing the first several.  I use various calculator admixture tools at GEDmatch that had the specific Oceania/Papuan/Melanesian category.  Dodecad World9 uses “Australian” instead. I created a column that totaled the average.  And the columns to the right of that shows those who tested at other companies and their Oceania percentages.  What is not shown in the list is the proportion of East Asian that would prove it does fall within the 27% – 32% Oceania.

The first row (in red) belongs to my mother, followed by my averages and then my brother’s.  The following lines in bold are for those at least 95% Polynesian.  I took the lowest and the highest percentages of Oceanian to see if it falls within the range consistent with the research.  Since these admixture calculators did not have just a single East Asia category alone, I listed the other categories that are known to split off from the East Asia category.

Eurogenes K9b
Oceania = 17.74%
Southeast Asian = 48.87%
Northeast Asian = 13.32%
Native American = 1.55%

Adding the Southeast Asian, Northeast Asian and Native American categories total 63.74%.  17.74% Oceanian makes up 27.8% of the total (East Asian compiled categories) of the Polynesian genome.  Consistent with the research.  Looking at the highest percentage.

MDLP World
Melanesian = 20.78%
East Asian = 56.31%
Artic Amerind = 1.65%
Mesoamerica = 0.13%

There was an Indian category showing 3.74%, but I did not add that in.  Adding it, changed the overall percentage to 33%, but leaving it out made it 35.7% of the Polynesian portion. For the others listed on that list, they also picked up a small 1 – 3% of the Indian category, and leaving it out made their average 30%.  If I look at the average column for all the admixture calculators for my mother, it comes out to 30%.

But what happens when there is a higher percentage of East Asian?  In my case, it is higher because my father was Filipino. My portion could easily be verified simply by removing 50% (my father’s contribution) from my average total of 85% East Asian giving me 35% East Asian that would be my Hawaiian/Polynesian side.  My average (GEDmatch) showed 32%.

There are many Hawaiians admixed with Chinese, Japanese, Filipino or Korean, being that they were all immigrant groups to the Hawaiian islands.  Are you able to tell if they have an Asian admixture?  Can it be distinguished from the East Asian that is part of the Polynesian genome?  This is something I have been seeing more now particularly with adoptees.

Any excess East Asian percentage  compared to the Oceanian percentage [79% to 21%], would indicate that the person is admixed with some other Asian ancestry.  Since my mother’s genome does not indicate any more East Asian than what it should for Polynesians, it is clear that she does not have any additional Asian ancestry.

Footnotes

1. Genome-Wide Analysis indicates More Asian than Melanesian Ancestry of Polynesians
2. Population Genetic Structure and Origins of Native Hawaiians in the Multiethnic Cohort Study

Loss of heterozygosity – from Western Polynesia to Eastern Polynesia

Genetic research on Polynesians will frequently mention the loss of heterozygosity.  This is more noticeable when comparing eastern Polynesians to western Polynesians.

oceania

Map outlining migratory paths of Austronesian speaking populations, including estimated dates. Adapted from Bellwood et al., (2011) “Are ‘Cultures’ Inherited? Multidisciplinary Perspectives on the Origins and Migrations of Austronesian-Speaking Peoples Prior to 1000 BC.” [doi: 10.137/journal.pone.0035026.g001

Polynesian populations are relatively homogenous both phenotypically and genetically. Over a span of 3,200 years they moved throughout the Pacific, and unlike in Europe and other large continents, they did not mix with other populations due to isolation.  These small founder populations have experienced several bottleneck effects, which further caused this loss of heterozygosity ending with the settlement of eastern Polynesia.  Polynesians’ lack of genetic diversity is less evident in western  Polynesia where initial settlement began.  Hawai’i, New Zealand and Easter Island are considered to be eastern Polynesia, and these places were the last places of Polynesia to be settled.

Recently I have been able to look at the autosomal matches among Samoans and Tongans of western Polynesia.  Previously, I have been only studying Hawaiian matches and noticed that top matches were both Hawaiians and Maori people.  Looking at Samoans and Tongans was very interesting as I now could compare the two different regions.

My mother is 80% Hawaiian, while I am 40%.  And as admixed as I am, I still get 1st – 3rd cousin predictions on Family Tree DNA (FTDNA), while on 23andme I get 2nd cousin and 3rd to distant cousin predictions.  The centimorgan totals that I show with my matches reach as high as 369cM on FTDNA, and 161cM on 23andme.  For my mother, 693cM on FTDNA and 376cM on 23andme.  I see the same happening with Maoris, ranging between 300cM – 700cM (FTDNA) for the top 20 people.  And for a non-admixed Hawaiian, their top matches are in the 600 – 700cM range.   An admixed Polynesian would logically have lower totals. But even an admixed person can still have a fairly high amount of totals shared, as when I am comparing myself being less than half Hawaiian.

When comparing two Tongans, the highest that they shared was 335cM.   A Samoan compared to another Samoan was 366cM.  And both of these Tongans and Samoans had their remaining top matches in the range of 100cM to 200cM.  Many of their matches are the same Hawaiians and Maori that match each other at a much higher total.  It is amazing to see these autosomal matches and how diverse the western Polynesians are, or rather how Hawaiians and Maoris are not as diverse.  And even if it is an admixed Hawaiian or Maori, the matches to each other are still pretty high, and as high as what non-admixed western Polynesians would have to each other.

When comparing the longest block (largest segment) with Tongans and Samoans, they seem to rarely get close to 15cM, averaging around 10cM.  Anything more than that could indicate a possible closer relationship or perhaps a specific common geographic origin.  The Hawaiians and Maoris usually range between 10cM – 15cM for the largest segment, but can go as high as 28cM which is usually in admixed Hawaiians and Maoris compared to each other.  In other words, all Polynesians in general will have high totals exceeding 100cM, but whose largest segment rarely exceeding 10cM.

I look forward to more western Polynesians getting tested so we can see if there is any pattern to specific islands in their own island group, something I have been trying to do with Hawaiians with the few haplogroups that there are for Polynesians.  What also needs to be analyzed are people from Tahiti and the Marquesas being that they were key dispersal points for eastern Polynesians.  I managed to only see the results of one admixed Tahitian woman and her match totals are identical to mine when comparing totals.  I am curious to find out what non-admixed Tahitians will show, if it is more identical to eastern Polynesians, or to western Polynesians.